1. Field of the Invention
The present invention relates to a camera system including a camera body and an interchangeable lens detachably attached to the camera body.
2. Description of the Related Art
In most SLR camera systems produced in recent years, the camera body is provided with a stop-down device for stopping down a diaphragm (iris diaphragm) of the interchangeable lens that is detachably attached to the camera body while the interchangeable photographing lens is provided with an automatic stop-down device which is actuated by the stop-down device of the camera body to stop down the diaphragm of the interchangeable lens. Such SLR camera systems are disclosed in, e.g., in the following publications: U.S. Pat. No. 5,602,616 (FIGS. 1 through 5), and U.S. Pat. No. 5,878,296 (FIG. 2).
In the interchangeable lenses having the aforementioned automatic stop-down device, various types of interchangeable lenses are known in the art: an interchangeable lens including a manual aperture setting device with which an aperture setting can be selected between an auto aperture setting (in which the aperture is set via the camera body) and a manual aperture setting (in which the aperture is set via the interchangeable lens), an interchangeable lens including a manual aperture setting device with which only manual aperture setting can be set, and an interchangeable lens including no manual aperture setting device.
On the other hand, in the camera bodies having the aforementioned stop-down device, some camera bodies cannot detect the f-number (aperture value) set by the manual aperture setting device of the interchangeable lens although being capable of inputting data on f-number at full aperture from the interchangeable lens. Namely, there is known a type of camera body which is not provided with any detecting device for detecting the f-number which is set by a manual aperture setting device of the interchangeable lens, e.g., by a rotational operation of the aperture setting ring (often marked in f-numbers) of the interchangeable lens in association with an aperture-setting ring member provided in the interchangeable lens.
In addition, among conventional SLR camera bodies, an SLR camera provided with a stop-down device which stops down the diaphragm of the interchangeable lens prior to a shutter release is known in the art. This type of SLR camera body is disclosed in the aforementioned Japanese patent publication No. 3153482.
However, in the case of a conventional camera body having no device for detecting neither the f-number at full aperture of the interchangeable lens nor the f-number set by the manual aperture setting device of the interchangeable lens, a correct exposure value cannot be set by actuating an exposure meter and a photometering device in association with the f-number set by the manual aperture setting device of the interchangeable lens.